Miguel Angel Soto Parra, arrested on Wednesday in Mexico City, is a former police officer who was one of the earliest members of the Zetas, a group of hitmen made up largely of army deserters, a source at the attorney general's office said. President Felipe Calderon has scored a number of big arrests since he sent the army to crack down on drug gangs. But turf wars have spiraled out of control, with some 5,650 people killed last year, many of them tortured or beheaded. The Gulf cartel, which relies on the Zetas to settle scores with rival gangs, is one of Mexico's top smuggling groups, running Colombian cocaine into Texas via the border cities of Matamoros, Reynosa and Nuevo Laredo, security officials say.